In ecological restoration of arid/semi-arid sandy lands, micro-topographic variations and artificial shrub arrangement synergistically drive vegetation recovery and soil quality improvement. As a typical fragile ecosystem in northern China, the Mu Us Sandy Land has long suffered wind erosion, desertification, soil infertility, and vegetation degradation, demanding precise vegetation configuration for ecological rehabilitation. This study analyzed soil nutrients, plant diversity, and their correlations under various micro-topographic conditions across different types of artificial shrub plantations in the Mu Us Sandy Land. Employing one-way and two-way ANOVA, we compared the significant differences in soil nutrients and plant diversity indices among different micro-topographic conditions and shrub species. Additionally, redundancy analysis (RDA) was conducted to explore the direct and indirect relationships between micro-topography, shrub species, soil nutrients, and plant diversity. The results show the following: 1. The interdune depressions have the highest plant diversity and optimal soil nutrients, with relatively suitable pH values; the windward slopes and slope tops, due to severe wind erosion, have poor soil nutrients, high pH values, and the lowest plant diversity. Both micro-topography and vegetation can significantly affect soil nutrients and plant diversity (p < 0.05), and vegetation has a greater impact on soil nutrients. 2. The correlation between surface soil nutrients and plant diversity is the strongest, and the correlation weakens with increasing soil depth; under different micro-topographic conditions, the influence of soil nutrients on plant diversity varies. 3. In sandy land ecological restoration, a “vegetation type + terrain matching” strategy should be implemented, combining the characteristics of micro-topography and the ecological functions of shrubs for precise configuration, such as planting Corethrodendron fruticosum on windward slopes and slope tops to rapidly replenish nutrients, promoting Salix psammophila and mixed plantation in interdune depressions and leeward slopes to accumulate organic matter, and prioritizing Amorpha fruticosa in areas requiring soil pH adjustment. This study provides a scientific basis and management insights for the ecological restoration and vegetation configuration of the Mu Us Sandy Land.

In the Mu Us Sandy Land, vegetation is closely related to soil microorganisms and nutrients. However, research on the relationship between soil microbial communities and nutrients in Pinus sylvestris var. mongolica plantations of different densities is still imperfect. This study selected Pinus sylvestris var. mongolica plantations with high, medium, and low densities, as well as bare sandy land, to analyze the relationship between vegetation density and soil nutrients, microbial community structure, and diversity indices. The results show that the following: (1) Medium-density plantations significantly increased soil organic matter, total nitrogen, and total potassium content, which were 4.3 times that of bare sandy land and 1.7 times that of high-density plantations; (2) In high-density plantations, the relative abundance of bacterial phyla Actinobacteriota and fungal phylum Ascomycota was higher; as plantation density decreased, the relative abundance of bacterial phyla Proteobacteria and Acidobacteriota and fungal phylum Basidiomycota increased, with different density plantations significantly affecting soil microbial community structure; (3) High-density plantations significantly increased the abundance of bacterial and fungal genera but also reduced bacterial diversity indices, while medium-density plantations were outstanding in enhancing fungal species richness and diversity, with the highest fungal Shannon index, indicating that medium density is conducive to fungal diversity enhancement; (4) Soil organic matter, total nitrogen, total phosphorus, total potassium, and pH value were the main environmental factors affecting soil microbial community structure. High-density plantations significantly affected soil microbial community structure by changing these soil nutrients and physicochemical properties, especially related to changes in total potassium and pH value. This study clarified the effects of Pinus sylvestris var. mongolica plantation density on soil nutrients and microbial community structure, revealing the intrinsic connection between soil nutrients and microbial communities, providing a theoretical basis for vegetation restoration in the Mu Us Sandy Land ecosystem, and helping to formulate scientific management strategies for Pinus sylvestris var. mongolica plantations to improve sandy land soil quality and promote the sustainable development of sandy land ecosystems.

To elucidate the effects of different plantation types on understory vegetation and soil properties in the Mu Us Sandy Land, this study investigated five plantation types: Pinus sylvestris var. mongolica Litv. pure forest, P. sylvestris var. mongolica-Salix psammophila C. Wang and Ch. Y. Yang mixed forest, Salix matsudana Koidz. pure forest, Amorpha fruticosa L. pure forest, and A. fruticosa-S. psammophila mixed forest, using bare sandy land as a control. Through quadrat survey and stratified soil sampling, we assessed the understory plant diversity, soil characteristics, and their interrelationships. The results showed the following: (1) A total of 11 understory plant species, belonging to 11 genera and five families, were recorded, predominantly shrubs from Asteraceae and Fabaceae, and perennial herbs. The S. matsudana pure forest exhibited the highest understory plant diversity, with Shannon and Margalef indices (1.72 and 1.87, respectively) significantly higher than other stands. (2) Soil nutrients varied significantly with forest type. The mixed forest of A. fruticosa and S. psammophila notably improved the contents of soil total nitrogen and organic matter, whereas the soil total phosphorus content was generally low in all stands. (3) Spearman correlation analysis revealed the differential responses of diversity indices to soil factors: the Simpson dominance index was significantly negatively correlated with 10~20 cm soil water content (SWC) (r = −0.9, p < 0.05), and significantly positively correlated with 20~40 cm total phosphorus (TP) (r = 0.9, p < 0.05), with no significant correlations with other soil factors (TN, TK, OM, pH); the Shannon diversity index was highly significantly negatively correlated with 0~10 cm SWC (r = −0.97, p < 0.01), and no significant correlations with other soil factors (TN, TK, TP, OM, pH); the Pielou evenness index was significantly positively correlated with 0~10 cm pH (r = 0.9, p < 0.05) and positively correlated with 20~40 cm pH (r = 0.8) (not statistically significant); by contrast, the Margalef richness index showed no significant correlations with all measured soil physicochemical factors. This study demonstrates that S. matsudana pure forest is more conducive to the development of understory plant diversity, and that soil factors exert a stronger regulatory effect on community structure (evenness and dominance) than on species richness in this arid sandy ecosystem.

Due to prolonged irrigation from the Yellow River, a large area of farmland in the Hetao Oasis has undergone different degrees of salinization and alkalization, leading to reduced crop yields and incapable soil for plant growth. To enhance the productivity of the farmland with saline-alkali soils, it is important to select salt-tolerant economic plant species that are capable of growing under the local climate and soil conditions in the Hetao Oasis. We conducted the experiment by planting Ziziphus jujuba var. spinose, Elaeagnus angustifolia, Hippophae rhamnoides and Lycium chinense in the Bayan Taohai Farm of the Hetao Oasis. Changes of plant growth (the survival rate, plant height, canopy, basal diameter and new branch length) and soil physicochemical properties (soil organic carbon, total carbon, total nitrogen, pH, electrical conductivity and particle size distribution) were continuously monitored during two growing seasons. Results indicated that, by the end of the first growing season, the survival rate of the Z. jujuba was less than 10%, making it unsuitable for plantation in the saline-alkali soils of the Hetao Oasis. In terms of plant growth, the E. angustifolia exhibited the highest survival rate (94.71%) and the fastest growth rate, indicating that E. angustifolia is adapted in the saline-alkali soils of the Hetao Oasis. The survival rates for L. chinense and H. rhamnoides were 86.46% and 65.64%, respectively, indicating that these species could grow in the saline-alkali soils, but at a slower rate. From the perspective of soil improvement, E. angustifolia, H. rhamnoides and L. chinense could reduce the soil pH, and E. angustifolia could significantly increase soil nutrients. In conclusion, it is not recommended to plant Z. jujuba, while the E. angustifolia is recommended as a proper economic species to be widely planted in the saline-alkali soils of the Hetao Oasis. H. rhamnoides could be selectively planted in areas with better soil conditions, and the L. chinense could be planted following soil improvement measurements. The research enhanced the effective utilization of the saline-alkali farmland and provided proper economic plant species for sustainable agriculture management in the Hetao Oasis of Inner Mongolia.

Mixed plantations of Pinus sylvestris var. mongolica with native shrubs are widely established in semiarid sandy landscapes, yet soil microbial responses may differ among mixed-planting modes depending on the companion shrub species. We compared soil bacterial and fungal communities across three approximately 9-year-old mixed-planting modes in the Mu Us Sandy Land, where P. sylvestris var. mongolica was combined with Juniperus sabina (Ps–Js), Salix psammophila (Ps–Sp), or Corethrodendron fruticosum (Ps–Cf). Planting configuration was associated with shifts in soil physicochemical conditions. Bacterial α-diversity did not differ among modes, whereas fungal α-diversity was higher in Ps–Sp. Community composition diverged across modes for both domains, and LEfSe identified configuration-specific taxa. Null-model analyses showed that bacterial assembly was consistently dominated by stochastic components, whereas the relative contributions of fungal assembly processes varied among mixed-planting modes. Functional inference further suggested mode-associated differences in fungal trophic guild composition, with Ps–Cf showing significantly higher ectomycorrhizal abundance and Ps–Sp showing higher representation of saprotroph-associated guilds; by contrast, predicted bacterial functional profiles were broadly comparable among modes. Together, these results indicate that bacterial and fungal communities showed different response patterns among mixed-planting modes: bacterial communities showed compositional differentiation but little variation in α-diversity and consistently stochastic assembly, whereas fungal communities showed mode-related changes in α-diversity, the relative contributions of assembly processes, and trophic guild composition. These findings provide a microbial basis for considering shrub-species selection when designing P. sylvestris var. mongolica mixed plantations in semiarid sandy ecosystems.